Metal coating process



, favor in the protective will have a temperature of Patented July 27, 1943 2,325,240 MIETAL COATING PROCESS Lowell o. Gill,

Decatur, Staley Manufacturing a corporation of Delaw 111., assignor to A. E. Company, Decatur, 111.,

are

No Drawing. Application October 5, 1940, Serial No. 359,909

1 Claim.' (Cl. 154-2) The present invention relates to an improved process for the protective coating of metals such as ferrous sheet material, and has particular reference to an improvement in the process of galvanizing sheet metal and combining the galvanized coating with asbestos paper.

A process which has met with considerable coating of sheet metal pipe consists in subjecting the metal to the ordinary galvanizing process and then combining the metal with an asbestos sheet while the molten zinc coating still i in a molten condition. Various types of asbestos papers have been employed for this purpose and the present invention has as a principal object the use of an improved type of asbestos sheet for combination withthe molten zinc of the freshly galvanized metal.

A further object of the invention is the provision of a process for protectively coating sheet metal in which the metal is provided with a galvanized coating of molten zinc and the moltensurface of the metal is combined with an asbestos fiber sheet having a protein sizing material. 1

- These and other objects will be observed upon consideration of the following description of a preferred embodiment of the invention.

The combining process by which the freshly galvanized metal surface is fabricated to an as-- bestos sheet is conducted at a high temperature. The molten zinc comprising the galvanizing layer the order of 850 F. At temperatures of this order any organic sizing material contained in destroyed. The nature of the resulting paper after. destruction of the size and the products of decomposition of the size determine the suitability of an asbestos paper for use in the process. Heretofore starch sizes have been employed for this purpose, since they provide an initially stronger asbestos paper. As it is somewhat difficult to produce a strong asbestos paper, this relatively high initial strength has been considered of importance. The present invention is based upon the discovery that substantially better results can be obtained in the process by the combination with the molten zinc layer of an asbestos paper produced with a protein size. Although the paper .may have less initial strength, I have found that after destruction of the sizing at the elevated'temperature involvedin the process the asbestos paper will provide a desirable combination with the zinc galvanized coating and at the same time the products of decomposition are much less objectionable than in the case of sizes known'heretofore.

the asbestos paper will be extent that Asbestos paper is of an alkaline nature, so that it has a beneficial dispersing effect upon the soybean size. Further quantities of alkaline material may be combined with the soy flour if desired.

As an example of the production of the asbestos paper, 130 pounds of soy flour was combined with 1300 pounds of water and the mixture was stirred until lumps were removed. The mix- ,ture then was heated to boiling. Sixteen hundred pounds of asbestos fiber were heat with 200,000 pounds of water and the soy flour suspension was added to the suspension of asbestos fiber. Thereafter the asbestos sheet was formed in the usual manner and dried.

In the galvanizing operation a sheet metal is passed through a galvanizing bath of molten zinc, from which it emerges at a temperature of around 850 condition.

F., the zinc still being in a molten Before the zinc is cooled to such an it solidifies, the asbestos sheet is pressed into firm engagement with the galvanized side of the sheet. The high temperature causes the protein size to decompose and the molten zinc partially impregnates the asbestos fiber to provide'a firm union between the asbestos sheet and the galvanized metal. complete the process.

Other preservatives such as hot bitumen may be used to impregnatethe asbestos sheet after it has been united to the galvanized coating of the metal.

The metal is cooled to An advantage in the use of a protein size for- In the process of protecting metal wherein said metal is subjected to a bath of molten zinc and while said zinc is stillin a molten state on the surface of said metal, applying a protective surface consisting of asbestos fibers, the improvement which comprises the step of applyingasbestos paperhaving incorporated therein a soybean flour size which will become decomposed when exposed to said molten zinc and which will The particular protein size used in the process eliminate pungent and objectionable odors and fumes.

LOWELL O. GILL. 

